{Newest 2 Versions} Exam Comprehensive Practice
Questions with Correct Answers and Detailed Explanations
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SECTION 1: SOIL CLASSIFICATION & IDENTIFICATION (Questions 1-35)
Q1. According to ASTM D2487 (USCS), a coarse-grained soil has more than 50%
retained on the No. 200 sieve, and more than 50% of that coarse fraction passes the
No. 4 sieve. If the liquid limit is 45 and the plasticity index is 22, how is this soil
classified?
A. SC (Clayey sand)
B. SM (Silty sand)
C. CL (Lean clay)
D. GC (Clayey gravel)
Correct Answer: A. SC (Clayey sand)
More than 50% of the coarse fraction passes the No. 4 sieve, making it a sand (S). The
Atterberg limits plot above the "A" line with a PI > 7, which designates the fines as clayey
(C), resulting in a classification of SC .
,Q2. A soil sample contains 58% sand, 32% silt, and 10% clay. Laboratory testing
indicates low plasticity. Under the Unified Soil Classification System (USCS), the soil
would most likely be classified as:
A. CL
B. ML
C. SM
D. SC
Correct Answer: C. SM
The soil is predominantly sandy with a significant amount of non-plastic or low-plasticity
fines. Under USCS, sands containing appreciable silt-sized particles and exhibiting low
plasticity are classified as SM (Silty Sand) .
Q3. A soil exhibits a liquid limit of 55 and a plasticity index of 30. The soil is most
likely:
A. CH
B. ML
C. SP
D. GW
Correct Answer: A. CH
A liquid limit above 50 indicates high plasticity. A plasticity index of 30 places the material
above the A-line on the plasticity chart, resulting in classification as CH (high-plasticity
clay) .
,Q4. During a standard visual-manual soil classification (ASTM D2488), a soil sample
ribboned between the thumb and forefinger reaches a length of 2.5 inches before
breaking. This behavior suggests high content of what particle type?
A. Silt
B. Clean sand
C. Clay
D. Fine gravel
Correct Answer: C. Clay
The ability to cast a long, continuous ribbon indicates high plasticity and cohesion, which
are distinctive physical properties of clay-rich soils .
Q5. What is the primary purpose of the Unified Soil Classification System?
A. Determine compaction equipment requirements
B. Estimate project costs
C. Categorize soils based on engineering behavior
D. Establish pavement thickness
Correct Answer: C. Categorize soils based on engineering behavior
USCS groups soils according to particle-size distribution and plasticity characteristics to
predict engineering performance. While classifications may influence equipment selection
and design, those are secondary applications rather than the primary purpose of the
system .
, Q6. A soil classified as "CL" under the USCS system is described as:
A. Clayey gravel
B. Silty clay
C. Lean clay
D. Fat clay
Correct Answer: C. Lean clay
"CL" stands for Inorganic Clay of Low to Medium Plasticity, commonly referred to as lean
clay .
Q7. According to ASTM D2487, when is a soil classified as fine-grained?
A. More than 35% passes the No. 200 sieve
B. More than 50% passes the No. 200 sieve
C. More than 65% passes the No. 200 sieve
D. More than 75% passes the No. 200 sieve
Correct Answer: B. More than 50% passes the No. 200 sieve
Per ASTM D2487, soils are classified as fine-grained when 50% or more of the material
passes the No. 200 sieve (0.075 mm) .
Q8. The coefficient of uniformity (Cu) is primarily used to evaluate:
A. Plasticity
B. Particle-size distribution characteristics
C. Moisture content
D. Shear strength